left-truncatable prime (another Prime Pages' Glossary entries)
 Glossary: Prime Pages: Top 5000: The hardware and software on this system was updated September 4th.  Please let me know of any problem you encounter. Left-truncatable primes (or just truncatable primes) are prime numbers (without the digit zero) that remain prime no matter how many of the leading digits are omitted. For example, 4632647 is left-truncatable because it and each of its truncations (632647, 32647, 2647, 647, 47, and 7) are primes. We omit the digit zero to avoid trivial examples such as the prime 1060+7: 1000000000000000000000000000000000000000000000000000000000007. Each of its truncations is the prime 7. The three largest left-truncatable primes are: ``` 959 18918 99765 33196 93967, 966 86312 64621 65676 29137, and 3576 86312 64621 65676 29137. ``` We leave it to the reader to find the largest such primes in other bases. References: AG1977 I. O. Angell and H. J. Godwin, "On truncatable primes," Math. Comp., 31 (1977) 265--267.  MR 55:248 Caldwell87 C. Caldwell, "Truncatable primes," J. Recreational Math., 19:1 (1987) 30--33. [A recreational note discussing left truncatable primes, right truncatable primes, and deletable primes.] Clark1973 H. J. Clark, "Letter to the editor," Computer Weekly,:360 (27 September 1973) 26. Chris K. Caldwell © 1999-2014 (all rights reserved)